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Evaluating iron deficiency
Monitoring treatment and environmental intervention of chronic
lead poisoning
The porphyrins are intermediaries in the heme synthesis pathway.
When iron is not available for heme synthesis (eg, iron deficiency),
zinc protoporphyrin (ZPP) accumulates within red blood cells (RBC).
Lead inhibits several enzymes in the heme synthesis pathway and
causes increased levels of RBC ZPP.
ZPP is a biological marker of lead toxicity and was previously used,
in conjunction with blood lead assays, to screen for lead poisoning
in children. However, because of poor sensitivity and specificity,
ZPP is no longer recommended for lead screening in children.
However, ZPP remains a useful tool for monitoring treatment of
individuals with confirmed elevated lead levels.
<70 umol ZPP/mol heme
An elevated ZPP indicates impairment of the heme biosynthetic
pathway.
In children, a blood lead level of >20 ug/dL and an ZPP level
of >70 umol ZPP/mol heme are indicative of lead toxicity.(1)
Elevated ZPP levels in adults may indicate long-term (chronic)
lead exposure or may be indicative of iron deficiency anemia or
anemia of chronic disease.
No significant cautionary statements
1. Stanton NV, Gunter EW, Parsons PJ, et al: Empirically determined
lead-poisoning screening cutoff for the Protofluor-Z hematofluorometer.
Clin Chem 1989;35(10):2104-2107
2. Rosen JF: Preventing Lead Poisoning in Young Children. US
Public Health Service, Centers for Disease Control, Atlanta,
GA, 1991
3. Occupational Safety and Health Administration: OSHA Lead
Standard - Requirements from the General Industry Standards
Lead (1910, 1025), from 29 CFR 1910, 1025, A.M. Best Safety
and Security - 2000. Retrieved March 2000. Available from URL:
ambest.com/safety/osha/chap10g.html
4. Centers for Disease Control and Prevention. Screening Young
Children for Lead Poisoning. Guidance for State and Local
Public Health officials. Atlanta, GA: US Dept of Health and
Human Services. Public Health Service: November 1997
Available from URL: cdc.gov/nceh/lead/guide/guide97.htm